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PDP 8e - OS/8 working enough to run for 2 hours.

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  • Bill Degnan
    PDP 8e project update David Geeswin stopped by the office last night to take a look at my PDP 8e system on his way home from a work trip. I described to him
    Message 1 of 3 , Jul 28, 2010
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      PDP 8e project update

      David Geeswin stopped by the office last night to take a look at my PDP 8e
      system on his way home from a work trip. I described to him how I had been
      having trouble interfacing the CPU using a terminal, and I was unable to
      boot from the disk drive.

      We ran a bunch of tests and determined that there was a problem with the
      I/O card (M8650) and the bootstrap loader card for the RK05. I was lucky
      enough to have a spare I/O card that worked a little better and Dave
      brought a printout of the code to manually bootstrap the disk drive. It's
      only two lines:

      The manual bootstrap loader for the RK05 is
      0030: 6743
      0031: 5031

      We were able to initiate a boot using the manual bootstrap, but there were
      too many garbled characters to have an effective OS/8 session. I was
      thankful to learn that the CPU and disk controllers were not the problem.

      *Today* for whatever reason the gods of computing smiled on me. I was able
      to boot the system into a stable OS/8 session which lasted for two hours.
      Why things remained stable today I can't say, but I loaded Adventure and
      played for a long time. I also loaded BASIC from disk and I was able to
      write and run simple programs from BASIC.

      Thank you David for your help! It was quite a joy to play Adventure on a
      PDP 8.

      Unpolished Videos (from Android phone) -
      http://www.youtube.com/v/TJdq3gK6M78
      http://www.youtube.com/watch?v=jcQ3zK1vZyc

      Bill
    • David Gesswein
      ... Good that you were able to use your system. The gods may be more of teasing you. Intermittent problems can be really annoying to fix. I spent 6 months
      Message 2 of 3 , Jul 29, 2010
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        > *Today* for whatever reason the gods of computing smiled on me.
        >
        Good that you were able to use your system. The gods may be more of
        teasing you. Intermittent problems can be really annoying to fix. I spent
        6 months trying to track one down in my PDP-8 since every time I touched
        it to try to trouble shoot the problem would go away. It ended up being
        a bad connection that got better for a while if the card was moved. Your's
        at least seems to stay acting up for a while.

        While its working you should see if you can write to the first 2
        locations of field 7 that we were having problems with to see if the
        two issues are related. Probably also good to run memory address (DHKMCB) and
        checkerboard diagnostics (DHKMAC). Adventure uses all the memory so if it
        works the memory is probably good.
      • B Degnan
        ... I agree, I should take advantage of moments of clean operation to run test programs. I will run these diagnostics next time, let you know how it goes.
        Message 3 of 3 , Jul 29, 2010
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          David Gesswein wrote:
          *Today* for whatever reason the gods of computing smiled on me.
          
              
          <snip>
          While its working you should see if you can write to the first 2
          locations of field 7 that we were having problems with to see if the
          two issues are related. Probably also good to run memory address (DHKMCB) and
          checkerboard diagnostics (DHKMAC). Adventure uses all the memory so if it
          works the memory is probably good.
          
          
          
            
          I agree, I should take advantage of moments of clean operation to run test programs.  I will run these diagnostics next time, let you know how it goes.
          Bill

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